Radiation detection device



Jan., 17, 1956l Filed Aug. 14, 1951 FIG. i.

G. FAILLA RADIATION DETECTION DEVICE 2 Sheets-Sheet l I N VEN TOR.

GIA aaHm/w FAILLA BMMW ATTORNEY Jan. 17, 1956 G. FAILLA4 2,731,563

RADIATION DETECTION DEVICE Filed Aug. 14, 1951 2 Sheets-Shea*` 2 mmm,

n' m MINIMUM.

N .QE

INVENTOR.

g1/TA @001L1/a EULLA B v @JMJ www Arran/5y United States Patent O RADIAToN DETECrloN nevica Gioacchino Failla, New York, N. Y., assigner to the United States of America as represented by the United States Atomic Energy Commission Application August 14, 1951, Serial No. 241,778

8 Claims. (Ci. Z50-83.3)

The present invention relates to an `apparatus for detecting the presence and relative intensity of ionizing radiation.

There Vare numerous devices which have been designed for the detection of ionizing radiation. For the most part these devices are designed for highly accurate radiation measurement and are perforce complicated, expensive and unwieldly. The present invention is directed toward a new type of device which although sacrificing of the accuracy of the more elaborate detection apparatus is capable of being manufactured in very compact form at relatively low cost. The present device has particulail utility in providing a gross indication of the presence of ionizing radiation in quantities which are dangerous or harmful to the observer. By suitable adjustment of the component parts, the apparatus may also be transformed into a more accurate detector comparable with the accuracy of the more cumbersome and conventional apparatus. The present apparatus has particular advantage for iield usage, as for example, for employment under conditions wherein the device is subjected to relatively rough treatment, or handled by comparatively unskilled persons, or used under varied weather conditions or the like. It also can be employedwhen nopower supply or sensitive charge detecting or quantitative measuring auxiliary apparatus is available since the present apparatus will function continuously without the aid of any auxiliary apparatus to give a continual reading of the presence or absence of dangerous amounts of ionizing radiation.

It is accordingly an object of the present invention to provide a compact apparatus capable of giving a gross indication of the presence of ionizing radiation in hannful quantities.

It is another object of the present invention to provide a radiation detection device which is capable of operation within a self-contained sealed container and without the aid of auxiliary voltage generating or detecting apparatus.

It is a further object of the present invention to provide a radiation detection device capable of adjustment of sensitivity over a relatively wide range. Y

Other objects and advantages of the invention will be in part obvious and in part pointed out hereinafter.

In one of its broader aspects the objects of the present invention may be achieved by providing a device for indicating the presence of ionizing radiation which essentially comprises a sealed container, containing a dielectric material, an ionizable gas, andat least one movable element within said container; the element being adapted to separate triboelectric charge by relative mou tion of said element and said dielectric, and a means movable by a triboelectric charge against an independ- .ent restoring force for indicating the charge developed by the vrelative motion of said movable element in said container.- .As will be apparent, the means movable by said charge separated by'said element may conveniently take the form of a second such element inuenced by the force of gravity.

lCC

In describing some of the embodiments of the present invention reference will be made to the accompanying drawings wherein:

Figure 1 is a horizontal sectional view of the interior of a radiation detection device containing a number of spherical elements shown in the charged state mutually repelling each other on a concave surface, the view being taken along line 1--1 of Figure 2.

Figure 2 is a vertical section taken on a line 24-2 of Figure 1 showing the concave surfaces of the two chambers of the detection device as well as the movable elements of different sizes in the respective chambers.

Figure 3 is a vertical section of a second form of the apparatus for carrying out the invention showing five chambers having movable elements respectively of .iive different sizes, the section being taken along line 3-3 of Figure 4.

Figure 4 is a horizontal section taken on a line 4-4 o Figure 3.

Figures 5 and 6 are vertical and horizontal sections respectively of a third form of apparatus showing a single cylindrical chamber device having sets of pellets of diierent sizes, the section of Figure 6 being taken along line 6-6 of Figure 5.

Figure 7 is a vertical section of still another form of apparatus suitable for carrying out the invention and wherein a frictional charging chamber of cylindrical or other suitable configuration is electrically connected to a filament charge detecting chamber spaced from the charging chamber.

Figure 8 is a vertical section of still another form of apparatus adapted to employ a dropping liquid as the element to separate the charge and which likewise has a separate charge detection chamber.

Referring now to Figures 1 and 2, one form of the apparatus comprises an invertible container 110 made preferably of a dielectric material and having formed therein two chambers and 120. These two chambers each have one concave surface, 102 and 112 respectively and are formed as depressions in the generally cylindrical container 110. The chambers are dened at their outer surfaces by ilat surfaced windows 166 and 116, here shown as being part of a transparent dielectric, and at their inner surfaces by the concave depressions 102. and 112.V Within each of the chambers a number of elements, preferably also of a non-conducting material, are sealed so that relative motion of the container and elements results in the separation of a triboelectric charge. Thus, for example in the chamber 160 a number of spheres 108 of glass, amber or other non-conducting material, each having approximately the same weight and size, Vrest upon the. concave surface 102 which forms one boundary of the chamber 100. A number of spheres 118 of smaller diameter are enclosed within the chamber 120. In the course of fabrieating the apparatus it is preferable to ensure that the gas enclosed within the chambers is dry when the chambers are sealed. The operation of the apparatus depends on the separation of a triboelectric charge byy the m07` tion of the spheres relative to the container Such a charge may exist on the spheres or on the chamber surface or both. When the spheres are uncharged gravity causes them to gather at the lowest point of the concave surface 1492 where they rest in contact with one another. If the 'apparatus is shaken so that the elements arecaused to move about within the chamber in contact with the walls thereof, a triboelectric charge is separated which causes the spherical elements to be displaced from'each lotherabout the surfacel of the chambers.A The larger f Y V2,731,568

The principal indication upon which an operator relies in employing this device as a radiation detection meter, is the separation or the failure of separation of the elements when and after the device is shaken. Thus, if a user is exposed to a field of radiation of higher intensity than that which the large sphere portion of the device is set to indicate, he will be unable Vto causen-iboelectric separation of the larger spheresl by shaking the device.Y This serves to give the user an instantaneous indication of exposure to radiation above a certain threshold danger-level. The intensity range of the radiation may then be roughly approximated by inverting the apparatus and by shaking and observing the behavior of 'the smaller set of spheres. In general, it is more diliicult to cause'rthe electrostatic separation of larger di- Y Y kameter than of smaller diameter spheres and therefore chamber 12). In this manner, he may determine'if the intensity of the field of radiation to which the apparatus is exposed is above Ya second Vand more critical danger level. The two sets of spheres of diierent diameters may be useful for example to indicate the presence of a predetermined dosage rate of radiation when the large YdiameterV spheres fail to charge, and of a greater radiation dosage rate when the smaller diameter spheres 118 fail torcrharge. VThe selection of spheres of differentV diameters and the employment of a larger number of chambers (as will be discussed below with refcrenceto Figure 3) withsuitable adjustment of the sensitivity of Vthe apparatus, permits the radiation intensity level to be Vdetermined within relatively close limits simply by causing frictional motion of the movable elements in the container. Itis thus apparent that the plurality of rspheres in Vthis embodiment mutually operate as both the triboelectric charge developing means and the charge in- Y dicating means.

In one satisfactory form of apparatus, such as that indicated in Figure. l, spheres of about 3 millimeters diameter were enclosed within a chamber having a concave surface, the radius of curvature of Vthe surface being about one inch. By shaking the container so as to impart a rapid motion of the spheres relative to the container a triboelectric charge was developed in the appajratus. This was apparent from the mutual displacement of the spheres by about 3 millimeters. The device failed Yto charge when shaken in a radiation eld of about 30 roentgens perhour.

A second form of apparatus is disclosed in Figures 3 and 4. ln this modification aV container 300 encloses five separate chambers 302, 304, l3&6, '308 and 31() conrstructed of 1a dielectric material which preferably is transparent, although non-conducting separate windows maybe used if desired. A set fof uniform diameter spherical ele-ments is sealed in each chamber but'no two 'sets of elements have the same diameter. The shaking of the apparatus causes a triboelectric charge to be Y separated in the chambers and this causes the elements to Y cling tothe verticalwalls of the respective chambers against the force of gravity. As is indicated in Figure 3, the smaller elements such as those in chamber 308 Ycome to rest at -a higher levelthan the largerrdiameter elements such as those in chamber 394 Ydue to the inter- Vplay of forces of repulsion and attraction resulting from the separation of triboelectric charges. This is anv indication bothof the ease with which the smaller diameter elements are separated fby .the `.development ofY triboelectric :charge andthe diiculty of Yremoving them from the wallsdue to the dispersal of the charge ,in a eld of ionizing radiation. Y Y t Y traction onto the walls of the chambers.

elements are easier to dislodge under the influence of ay radiation field, but other factors, also, influence the re- In the operationof the apparatus illustrated in Figures 3 and 4 an operator who Wishes to test whetherhe is in a eld of ionizing radiation shakes Vthe device so as to bring the spherical elements into moving contact with the walls of the chambers. He is able to determine the level of the radiation intensity to which he is exposed by observing the level at which the elements in the chambers are retained on therwallswhen the shaking is stopped. Thus, for example if he observes that the larger elements in the two chambers on the left do not Vcling to the vertical walls of the chambers but that the elements in the three chambers of the right do separate and cling to the vertical walls of these chambers, he is made vaware that radiation intensity towhich he is exposed is above that which will prevent retention of elements on the Walls of chamber 304 but below that which will prevent retention of the elements on the Walls of chamber 386. By prior calibration the observation of the resulting location of the elementsA in the respective chambers will tell the observer the level of radiation. A useful range of'diameters for such elements is from about 0.1 to about 1.0 millimeter. As an alternative to the incorporation of such different diameter elements, elements of different densities may be incorporated. These have the same utility in indicating radiation intensity because the heaviergelements are more ditlcult to'suspend against the force of gravity by electrical at The heavier spouse.

Turning now Vto Figures 5 and 6 another form of the apparatus, containing two sets of movable chargeable elements Within the same container, is shown. The apparatus preferably consists of a plastic dielectric, transparent housing 500 enclosing a chamber 501.V The housing may have aV generally cylindrical shape and may be formed by sealing a top plate 503 at its periphery on to the upper tubular wall of the main portion of the housing 500. In this embodiment of the invention two sets Y of spherical elements, a larger set 502 and a smallers'ct 594 are sealed into the chamber 501. By shaking the device a motion is imparted to the elements 502 andV 504 relative to the container which causes them toV move about in frictional contact with the inner surface of the container.V Such motion causes the separation of a tri- Vboelectric charge withinthe container such that-they ele.-

ments are mutually-repelled andVV displaced from each other, are suspended against the force of gravity, and t tend to adhere to the internal vertical walls of the container 50i). When such a device is shaken'inY a eld of ionizing radiation of sufficient intensity the vtriboelectric charge will not be developed. 'Thus,'the .displacement of the chargeable elements 502 about the internal walls of Vthe container' or their failure to be displaced serves as an indication of the strength ofthe neld in which the shaking motion is imparted to thel device. As a general rule, it is found that Vfor elements of the same materialV Vthe smaller diameter elements are able to cling to'theV vertical walls of the container moreY easily than theheavy elements (as pointed out with respect to Figures V3 andk ratus'.v It consists :generally of afcup shapev metal clement'708 the lower portion 'ofthe chamber a number of movable spherical elements f714.sea1d wit.h in the chamber. A motion isimparted to these'e'l'ement's' to Vcharge the device preferabiy by moving vthe device laterally in a generally circular motion. This motion causes the separation of a triboelectric charge because the elements move in frictic nal contact with the upper plastic portion of the chamber 704. When the motion is stopped the charged elements fall to the metal cup portion 708 of the chamber. They may remain separated by mutual repulsion on the curved inner surface of the cup 70S but in any case the charge developed by their motion is retained in the device. The presence of the charge is indicated by the movement of the electrometer ber 712 in chamber 706. This iiber moves pivotally from the conductive rod 710 which is sealed in the wall 702 in electrical contact with cup 7 08. The rod 710 acts as one plate of a condenser in the chamber 706, the other plate being formed as a conductive coating, not shown, on the internal vertical and lower surface of the chamber 706. An electrically conductive substance such as Aquadag or evaporated aluminum is preferably used for forming this electrode coating The development of a charge on rod 710 by the lateral shaking of the device results in the establishment of an electric field in chamber 706 between the condenser plates or electrodes. Ion pairs formed in this field by radiation penetrating the chamber are separated and attracted to the electrodes. Thus the eect of radiation penetrating the device s the neutralization of a charge developed therein or the prevention of its development. A suicient portion of the transparent plastic Wall of the chamber 706 is left free of the conducting substance to permit viewing the position of the iilarnent 712 with respect to a scale 716. In order to discharge the device a grounding key 718 is provided at the lower portion of the chamber 706. This key is electrically connected with the chamber exterior through a conducting element 722 sealed through the wall 700 of the chamber. An abutment 720 is provided at the lower end of rod 710 to insure that the key will not be completely removed from its position of support in the lower Wall of the chamber when the device is inverted, but will fall into electrical contact with rod 710. In using the device it is charged by holding it in a vertical position and shaking it laterally, preferably with a circular lateral motion, to cause the elements 714 to move in the chamber 704 in contact with the internal walls thereof. As the elements move about the walls a triboelectric charge is separated and the elements become charged. When the device is no longer shaken these elements come to rest in the cup portion 708 of the chamber 7 04 and cause a charge to be transmitted through the rod 710 as indicated by the movement of the filament 712 with respect to scale 716. Under normal conditions the filament 712 will remain in the charged position for an extended period of time. Howeverwhen the device is shaken in a field of ionizing radiation, the movement of the iilament 712 to its uncharged or rest position will occur much more rapidly after the device has been charged. The rate of movement of the filament 712 is greater for more intense fields of radiation and thus may be used as an indication of the radiation intensity. For very intense fields the device will fail to charge at all when shaken. The device may be discharged and the procedure repeated simply by inverting the apparatus and proceeding with the shaking as hereinabove described.

Referring now to Figure S still another form of the apparatus consists of a plastic transparent housing 800 enclosing an upper liquid charging portion and a lower ionization portion electrically insulated from each other. The upper portion consists of a funnel element 802 having a relatively narrow bore outlet 806. A liquid 304 in the funnel falls by gravity to form individual droplets 805 as it leaves the outlet and these droplets irnpinge on an inverted conical element 808 of dielectric material supported by a rod 810 beneath the outlet 806. The drops 80S, serving the purpose of the spheres or movable elements in the preceding modifications, become charged by their contact with the conical element 808 and form droplets 807. These charged droplets fall to and are caught by a cup-shaped element 809 which is supported and sealed about midway in the container 800 against the internal vertical walls of the generally cylindrical container. This contines the liquid into the upper portion of the container. The droplets collect in the cup 809 as a liquid deposit 814. In order to return the liquid to the upper funnel member 802 the apparatus may be inverted to enable the liquid to iiow through the port 815 into the chamber formed within the funnel 302. In has been discovered that it is possible to develop a charge on a well insulated conducting element such as 809 by permitting a liquid such as mercury to flow in droplets from an upper element into the element to be charged. It should be noted that if the mercury comes out of ,the outlet 806 in the form of a stream, it is nevertheless broken into droplets upon impinging on conical element 308. Such an accumulation of charge on the cup 809 is indicated by the displacement of the filament 818 from the rod S16. This rod is attached into and extends downward from lower portion of cup 809. A scale 820 is provided to measure the extent of the movement of the filament 818. The internal horizontal and the lower vertical surfaces of the chamber formed beneath the cup 809 are made electrically conducting by applying thereto a conducting substance such as Aquadag or evaporated aluminum, suitable portions of the transparent housing of the lower chamber being left uncoated to provide visual inspection of scale 820. The portion of the internal vertical wall surface proximate to the cup 809 is also left free of any conducting substance so that the cup 809-is maintainedrin insulated relation within the container 800. Once the rod 816 has become charged due to the development of a charge on a cup S09 this lower portion of the apparatus acts as an ionization chamber. The rod 816 and its electrically connected portions may become discharged by a separation of ion pairs in the gas ambient to this rod by ionizing radiation which penetrates the container 800. The operation of this portion of the device as an ionization chamber is similar to that described with respect to chamber 706 of Figure 7. The discharge of the rod 816 and its electrically connected portions may also be brought about by inverting the apparatus to bring the grounding key 822 into contact with the lower portion S24 of the rod 816. Electrical connection ofthe grounding key 822 with the container exterior is made through the conducting element 826. Thus the inversion of the apparatus serves to discharge the rod 816 and cup 809 and also serves to return the liquid 814 'deposited in the cup 809 to the funnel S02. When this device is operated in a radiation field, charge accumulates in element 809 as the charged droplets fall into it. Atthe same time charge is carried away from it by the ions formed byA the radiation in the gas within the container. The same amount of liquid in the form of droplets passing into cup 809 delivers to it essentially the same amount of charge in the time that it takes to ow through orifice 806. In the same time ionization in the gas removes a certain amount of charge from the same system, being greater the p higher the intensity of the radiation. Therefore, the net charge at the end of the flow of liquid depends on the intensity of the radiation. Hence the maximum deflection of element 810 on scale 820 at the end of the running cycle is dependent on the intensity of radiation. Accordingly, the scale can be calibrated in terms of dosage rate, for instance roentgens per hour, for the maximum excursion of element 81S. It is clear that after all the liquid has passed into cup S09, charge will continue to be carried away from it by the ionization and element 818 will gradually return to the discharged position. The rapidity of this motion can be used as an additional measure of the intensity of radiation, especially for low values. Obviously, if the radiation intensity is very high charge is carried away by ionization as fast as itis brought sealed container.

to cup 809 by the liquid droplets `andthe system does not charge. However, jby l.suitable design vthe radiation intensity at which this will occur can be made as high vas desired.

In general, with respect to the operation ofthe devices contemplated'by the present invention the motion of a movable element in contact with surfaces hermetically Ysealed within the container causes the separation of ya charge within this container. ionizing radiation which penetrates the apparatus causes chargedrparticles to be formedwithin the apparatus. The ions become separated under 'the inuence of the developing charge and tend to neutralize it.

Y From the foregoing it is apparent that the device is capable of `self-contained operation in a hermetically Thus it is not necessary for any charging, discharging, or charge indicating or measuring devices to penetrate the sealed external container Vin order torender the device operative. The charge generating means as well as the charge indicating means are sealed Within the container. The scope of the l'present invention vincludes the devices wherein the charge developing and Vcharge indicating means are identical and wherein they are separate. Y

VFrom the foregoing it is also apparent that the present invention provides a very compact and economic ap` paratus. It will be understood that Vthe several forms .of `therapparatus as set out are given for illustrative purposes and that the concept of the present invention is not `limited to the illustrations given.

I claim:

Vv1. A device for indicating the presence and intensity of ionizing radiation which comprises a sealed container containing a dielectric material, an ionizable gas within said containenat least one small spherical element within .said container free to move in said container in contact with the dielectric material to Vseparate triboeiectric charge and at least another vsuch spherical element within said container being adapted to be displaced by said charge against the force of gravity.

2. A device for indicating thepresence and intensity of ionizing radiation which comprises a hermetically sealed container having a plurality of chambers each containing a dielectric material, anrionizable gas within each of said chambers, a first movable element within each of said chambers, adapted to separate triboelectric charge by relative motion of said element and said dielectric material, and at least Vone second ,element in each chamber being Vionizing radiation which comprises a hermetically sealed container, containing a dielectric material, an yionizable gas within said container, a liquid adapted to separate triboelectric charge by relative lmotion of vsaid liquid Aand material and means movableiby the triboelectric charge developed, against an independent restoring force, for 'indicating the charge developed by the relative motionfof said liquid 'within said container.

6. A device for indicating the presence and intensity of ionizing radiation which comprises a hermetically sealed container divided bya chargeable separating wall into Van upper and a lower chamber, said lowei chamber containing an ionizable gas, vsaid upper chamberV being provided with a fluid dispensingfunnel disposed torelease fluid onto a drop producingV member containing a dielec. tric material and ypositioned beneath the funnel outlet, lan opening near the upper portion-of said duid dispensing.

funnel, and means extending from said wall into said lower chamber for indicating the charge .developed'on Vsaid separating wall.

7. A device for indicating the presence and intensit of ionizing radiation which comprises arscaled container containing a dielectric material, an ionizable Agas within said container, a plurality of movable elements of dif- `ferent weights adapted to separate triboeleetric charge by Vrelative motion of said elements and said dielectric material, said elements being movable by a triboelectric charge against the force of gravity to indicate the per-v sistence of Va charge developed by Asaid motion relative to the ditferent weights of-said elements.

8. A device for indicating the presence and intensity of 4ionizing radiation which comprises a sealed container containing `a dielectric material, Vanionizable gas Within said container, la plurality -of movable elements of different sizes adapted to separate trjiboelectric charge `;by relative -motio'n of said-e1ements and -saiddielectn'c material, Vsaid elements vbeing movable by Va Vtriboelectric charge against the force of gravity to indicate fthe-per Vadapted to be displaced by said charge against the force l Y of gravity.

V'within said container, adapted toV separate triboelectric charge by relative motion of said elements in said container and at least one second element within said chamber adapted to be displaced and ysuspended upon said concave surface against the force of gravity.

'4. A devicefor indicating the A'presence and intensity i.

YYof ionizing radiation which Acomprises a hermetically sealed container divided by an internal separating wall sistence ofa chargev developed yby said motion relative to the differentsizes of Vsaid elements.

References Cited in the 'tile of this Apatent I'JNLTED STATES PATENTS 

1. A DEVICE FOR INDICATING THE PRESENCE AND INTENSITY OF IONIZING RADIATION WHICH COMPRISES A SEALED CONTAINER CONTAINING A DIELECTRIC MATERIAL, AN IONIZABLE GAS WITHIN SAID CONTAINER, AT LEAST ONE SMALL SPHERICAL ELEMENT WITHIN SAID CONTAINER FREE TO MOVE IN SAID CONTAINER IN CONTACT WITH THE DIELECTRIC MATERIAL TO SEPARATE TRIBOELECTRIC CHARGE AND AT LEAST ANOTHER SUCH SPHERICAL ELEMENT WITHIN SAID CONTAINER BEING ADAPTED TO BE DISPLACED BY SAID CHARGE AGAINST THE FORCE OF GRAVITY. 